#include  <stdio.h>
int main(void)
{
    int N=15, number, top, bott, mid;
    int a[15] = { -3,-1,0,1,2,4,6,7,8,9,12,19,21,23, 51};
    top = 0;
    bott = N - 1;
    scanf("%d", &number);
    while(top <= bott)
    {
        mid = (top + bott) / 2;
        if(number == a[mid])
        {
            printf("%d\n", mid + 1);
            break;
        }
        else if(number < a[mid]) bott = mid - 1;
        else top = mid + 1;
    }
    if(top > bott) printf("not found\n");
    return 0;
}
